Pollution of the Caspian Sea.

The pollution of Caspian Sea waters and bottom sediments was described on the basis of long-term monitoring data from 1978 to 2004. It was shown that in the 1980s total petroleum hydrocarbons were in high concentration in the estuarine waters of the Ural River, in the western part of the North Caspian, and near the town of Izberbash on the Dagestan coast, but later they reduced drastically everywhere. In contrast to water in the bottom sediments, zones of high concentrations of petroleum hydrocarbons were located in shallow areas adjacent to the Volga delta and in the western part of the North Caspian, where fine sediments occurred. The other part of the North Caspian, with mainly coarse sediments, had rather clean bottom material. The high concentrations of phenols and detergents in the water occurred rather often at the beginning of the period but later decreased significantly. No seasonal trends and spatial features were observed in their distribution. The average concentration of ammonium was high in the estuarine areas of the Volga, Terek, and Sulak rivers. In water, among the chlorinated pesticides DDT dominated. All pesticides were much more abundant in the 1980s than in the 1990s. In the bottom sediments, pesticides accumulated near the Volga River delta and were practically absent in the central part of the North Caspian. The heavy metal concentration was in the range of regional background levels. In general, for all kinds of pollution studied for this area, there were marked small-scale patches in time and space of very high concentrations. [ABSTRACT FROM AUTHOR]